You leaving disrupts kitty's routine and he also seems to have a little separation anxiety
Besides enough food and water and a pristine litter box when you leave, I'd get some toys around that he can play with indefinitely that don't require you there and can't get pushed under the couch far enough that he can't get em out. Fish on a string hung from the wall, ball in a track type things. Cover em in catnip, put catnip inside, whatever, so kitty will want to fuck with em. Just get enough things so he will be distracted for a day or two, have an outlet for all the energy the disruption of you leaving will unleash